My instinct (after not exploring this in much detail) is that you will get some improvements, if you don't blow past the memory limits of LLVM. I believe the 16 MB limit is gone, which will help, but you're still talking about deserializing plenty of bytecode for LLVM to process.

However Reini and I disagree about some things, I think we both agree that improving the typefulness of Perl code to narrow down the dynamic possibilities offer more potential improvements for memory use and optimization. That is probably also compatible with LLVM, but I still think to get real advantages out of LLVM, you have to port the VM to generate IR internally rather than compile the C components to IR with clang.